Synonyms for Pile Up (same or very similar meaning)
WordNet sense 1 (get or gather together):
accumulate, amass, collect, hoard, compile, collect, roll upWordNet sense 2 (arrange into piles or stacks):
heap up, stack upWordNet sense 3 (collect or gather):
conglomerate, gather, cumulate, conglomerateFrom the ODE community, based on WordNetadd/edit